Don't vomit her anymore, once should have been enough, its very risky. Don't give her yogurt for probiotics, this can cause more mucous, go to the dollar store and get a probiotic pill or powder and crush it up (if its a pill) and put it in the feed she's eating.
When you go to the vet tomorrow, bring a fresh fecal sample and tell them that they would be looking for eggs that look very much like the same eggs that you would find in dog or cat feces.
Your feed store lady is wrong. Fenbendazole or valbazen are the best thing to give. Once your vet does a fecal flotation, he or she will be able to pinpoint the best anthelmentic.